From Halopedia, the Halo wiki
The white weapons glitch is a graphical error seen when playing Halo: Combat Evolved on an Xbox 360. There are piles of dead bodies scattered in the levels before 343 Guilty Spark, with ammo and health packs. If the game is played on the Xbox 360, these piles of weapons are often colored white instead of their standard colorations.
As Halo: Combat Evolved was originally made for the Xbox, most of the theories presented here focus on the specific act of playing it on another console, as the Xbox 360 does not feature true backwards compatibility, but instead emulates every game that can play on it.
- One theory for this bug is that the Xbox 360 fails to load the textures of the weapons.
- This bug could be the result of the different programming and graphic styles between the original Xbox and the Xbox 360.